NO20150714A1

NO20150714A1 - A ventilation and safety apparatus

Info

Publication number: NO20150714A1
Application number: NO20150714A
Authority: NO
Inventors: Finn Wichstrøm; Eric Duault
Original assignee: Aker Engineering & Technology
Priority date: 2012-11-09
Filing date: 2015-06-03
Publication date: 2015-06-03
Also published as: NO335187B1; WO2014073978A3; NO20121324A1; WO2014073978A2; CA2890856A1; RU2015121898A

Description

A ventilation and safety apparatus

Field of the invention

The invention concerns shielding, ventilation and pressurc-relief devices for regions that are at least partially enclosed, as specified in the preamble of claim 1.

Background of the invention

Offshore installations used for production and processing of hydrocarbons from subterranean wells need aeration, particularly in regions on the installation where hydrocarbons are under pressure. These regions rely on abundant airfiows that serve to dilute any explosive mixtures of air and leaking hydrocarbons. In geographical areas with moderate winter (lower) temperatures, the need for controlling the influx of air into hydrocarbon-processing regions on the installation is not significant: aeration by natural ventilation (i.e. from ambient wind) is for the most part sufficient. The situation is different in arctic regions, where the climatic conditions are such that the work environment from time to time may be outside of applicable rules and regulations. Therefore, in arctic regions it is often necessary or desircd to reduce the aeration (i.e. airflow) caused by the ambient prevailing winds such that inspection and maintenance work may be planned and performed within acceptable standards. It is, however, also necessary and required to be able to quickly relieve the pressure caused by any explosion in these regions on the installation.

Fire and explosion in a processing plant are severe threats to this type of plants and the installation. An explosion in e.g. an offshore oil installation or gas installation may claim vast losses of human lives and render the installation inoperable for a long time. There are ex ampi es of such accidents causing entire installations to be permanent] y discarded. Considerable effort is therefore put into avoiding the occurrence of such accidents and to limit the extent of damage. Some of the most important means in that respect are good safety and maintenance routines and a fire extinguishing system with large capacity. However, even if safety and maintenance routines are thoroughly followed, the occurrence of an explosion or a fire is possible.

In hydrocarbon exploration, production and processing in the Arctic, there is also a des ire to protect equipment and personnel from strains resulting from adverse weather, temperature and wind. Tests have shown that that human personnel can work on an open deck for a maximum of 20 minutes under the extreme conditions that may be present in the Arctic. It is therefore desired to enclose the installation by means of weather louvers or windproof walls. However, such enclosing structures may have the adverse effect of causing damage to personnel and equipment in the event of an explosion, because the structures contribute to reducing the natural ventilation and effectively augmenting the local pressure increase caused by the explosion.

The state of the art includes WO 2008/033036, which describes an arrangement for reducing harmful cffects from fire and/or explosion. The arrangement comprises wall elements that are placed in adjacent relationship to one another to form a continuous wall. The elements are adapted to, when an explosion occurs, open the area towards the surroundings until the pressure in the area is balanced in relation to the surroundings. Thereafter the elements retum to their closed state to enclose the area to the surroundings, preventing air from the surroundings from entering the enclosed area and prevent fire extinguishing fluids from exiting the enclosed area. The elements comprise an elastically deformable material so that when the element is forced open, elastic energy is stored in the element to rapidly retum the element to the closed state.

The state of the art also includes FR 2 969 115 Al, which describes a ventilation and safety device for a wall of an onshore or offshore industrial facility. The device has a rectangular frame that comprises a security panel, and another solid permanent fixed panel that is provided in an integral manner with the security panel. A movable third panel is capable of sliding in a longitudinal direction behind the latter panel to create an opening in the frame. A motori/ed sliding unit, e.g. a linear actuator, is supported by the frame and cooperates with the movable panel to enable longitudinal sliding.

The state of the art also includes WO 2011/084071 Al, which describes a device for shielding operation areas and maintenance areas. The device comprises a frame for attachment in a wall structure and one in the frame pivotable supported panel. The panel comprises two substantially plate Uke panel parts attached to a common central member, and a device for pivoting the panel between open and closed positions. The panel further comprises a top plate and a bottom plate, between which the central member and two side raembers extend. The two panel parts are releasably attached to a respective one of the side members, and the top plate and bottom plate are pivotable within limits with respect to a substantially vertical axis in the area of the central member. The axis also substantially coincides with the pivot axis of the panel in the frame.

It is a need for a device and a method that adequately protects personnel and equipment from the environment surrounding the offshore installation (wind, rain, etc.), while also maintaining the natural ventilation and effectively preventing local pressure increases caused by explosions.

Summary of the invention

The invention is set forth andcharacterized inthe main claim, while the dependent claims describe other characteristics of the invention.

The purpose of the invention is to achieve a shielded area which allows natural ventilation and mitigates or avoids a pressure build-up in the event of an explosion.

It is therefore provided a ventilation and safety apparatus for a facility håving a shielded region at least partially defined by enclosing elements; said apparatus being arranged so as to delimit the shielded region from a region outside the facility. The apparatus comprises a sheet-shaped covering element substantially covering an opening between the regions and håving a plurality of apertures allowing fluid flow between the regions; and a stationary structure håving a substantially planar configuration and comprising an open grid structure in order to allow fluid flow through the stationary structure; the stationary structure furtherraore being arranged proximal to the covering element on the side of the covering element facing the shielded region; wherein the covering element and the stationary structure being arranged in a substantially parallel relationship with a distance between thcm, and arranged such that the stationary structure provides a support for at least a portion of the covering element when the latter is pressed towards the shielded region.

In one emtodiment, the covering element comprises at least one wcak region that is designed to be the first region of failure for the covering element.

In one embodiment, the covering element comprises sections håving apertures of different sizcs, and the area of each section corresponds substantially with the area of the opening.

In one embodiment, the covering element is movable with respect to the opening, so as to arrange a selected one of the sections in the opening.

The covering element is in one embodiment supported by and movable by rollers arranged on opposite sides of the opening; the rollers being configured for storing at least a portion of the covering element that is not being arranged in the opening.

Removal devices are preferably arranged proximal a respective roller and configured for removing substances such as snow or ice before the covering element is rolled onto a respective roller.

In one embodiment, a secondary apparatus is arranged on the side of the stationary structure facing the shielded region; said secondary apparatus comprising a secondary flexible element håving at least a baffie section with a plurality of holes that are configured to reduce the speed of the wind coming from the outside region and stop unwanted substances from entering the shielded region. The secondary flexible element is preferably movable so as to selectively arrange the baffie section in alignment with the opening.

In one embodiment, at least one heater is arranged on the side of the stationary structure that faces the shielded region.

In another embodiment, the covering element comprises a plurality of transverse laths.

In another embodiment, the apparatus further comprises a plurality of vertical ribbons, wherein the transverse laths together with the vertical ribbons structure the covering element in a plurality of grid fields, wherein the at least one weak region comprises rupture lines which extend from the corners of the grid fields towards the centers of the grid fields, respectively.

The invention utilizes the prevailing winds outside the installation to aerate a shielded region on the installation in a controlled manner. The invention also prevents environmental substances such as snow, rain, sleet and ice from entering the shielded region. The invention is also a safety device that is designed to open when exposed to blast loads in the shielded region, thereby preventing or at least mitigating pressure build-up in the shielded region.

Brief description of the drawings

These and other characteristics of the invention will become clear from the following description of a preferential form of embodiment, given as a non-restrictive example, with reference to the attached schematic drawings, wherein: Figure 1 is a cross-sectional side view of the shielding device according to a first embodiment of the invention; Figure 2 is a front view showing a section of an embodiment of a first covering element; Figure 3 is a cross-scctional side view of the shielding device according to a second embodiment of the invention; Figure 4 i s a front view showing a section of an embodiment of a second covering element; Figure 5 is a cross-sectional side view of the shielding device according to a third embodiment of the invention, and Figure 6 is a front view of another embodiment of a first covering element according to the invention.

Dctailed description preferred embodiments

The following description uses terms such as "horizontaT, "verticar, "lateral", "back and forth", "up and down", "inner", "outer", "upper", "lower", etc.

These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal operation of the device. The terms are used for convenience only and shall not be limiting.

The following description refers to equipment and processes on an offshore installation configured for exploration, production, processing and/or storage of hydrocarbons. Such installations are not described in detail here, as they per se are well known in the art. For the purpose of this description, it suffices to note that the invented device is configured to be arranged on an offshore installation (not shown) in a manner so as to serve as a shielding barrier between a shielded region on the installation (e.g. a proccss deck) and the environment surrounding (i.e. outside of) the installation.

A first embodiment of the shielding device 30 is illustrated schematically in figure 1. A shielding device 30 is arranged between a shielded region A (e.g. a process deck on an offshore installation) and the environment surrounding the offshore installation (not shown). The environment is denoted by reference letter B and hereinafter also referred to as the "outside region". In practical applications, the shielding device may therefore be placed at the outer perimeter of the offshore installation, serving as a barrier between the surrounding environment of the outside region B and the more or less enclosed shielded region A. The shielding device may therefore be subjected to e.g. wind, rain (often supercooled), snow and sea spray from the outside region B.

The shielding device 30 comprises a flexible covering element 1 connected to and stretchcd between two rollers 3a,b, such that an exposed portion 32 of the covering element is facing the outside region B. In the illustrated embodiment, the covering element comprises an elongated flexible fabric material. For the purpose of this description of the illustrated embodiment, the covering element will generally be referred to as "sheet". It should thus be understood that the covering element 1 may comprise fabrics (woven or non-woven), shecting, foils or membran es.

The sheet material is windproof and of a tear resistance that is dimensioned to withstand the design environmental loads (wind force, wave impact, etc.) for the given application. The sheet 1 material is preferably non-adhesive, such that sleet, snow and ice do not stick to and accumulate on the exposed sheet portion 32.

The rollers 3a,b are aligned and in the illustrated embodiment attached to upper and lower structures, respectively. In figure 1, reference number 4a denotes an upper deck structure, and reference number 4b denotes a lower deck structure. Thus, the exposed sheet portion 32 covers the area between the upper deck 4a and lower deck 4b, and serves to protect the shielded region A (håving e.g. processing equipment) behind. Although not specifically shown the figures, it should be understood that the axial length of the rollers correspond to the width of the sheet 1. The sheet 1 has a length that exceeds the dimension of the opening O between the shielded region and the outside region, thus allowing parts of the sheet to at any given time being stored on both rollers 3a,b. The sheet 1 may thus be moved up and down as indicated by the double arrow in figure 1, by rotating the rollers 3a,b. The rollers 3a,b may be rotated manually or by a control system comprising at least a motor (not shown). Thus, by operating the rollers, different portions of the sheet 1 may be exposed to the outside region B; i.e. changing the exposed sheet portion 32.

The shielding device 30 further comprises upper and lower scraping deviccs 5a,b, each arranged in the vicinity of a respective roller 3a,b. The scraping devices 5a,b are adapted to remove snow, sleet, freezing rain or ice from the exposed sheet portion 32 when the sheet 1 is being moved between the rollers. The scraping devices may be fbced at a small distance from the sheet, or may be a trailing scraper.

Figure 2 shows a portion of an embodiment of the sheet 1. Reinforcing wires 27 extcnd the length of the sheet, one on each side. A suitable groovc (not shown) that is shaped and dimensioned to accommodate the wire is provided on both ends of each roller. This ensures a stable and controlled movement of the sheet. A number of rupture lines 6 extend across the sheet 1. Some rupture lines are arranged in the sheet-Iongitudråal direction, others in its transverse direction. The rupture lines are dcsigned to be the first location(s) of failure for the exposed sheet portion. Thus, when the exposed sheet portion is subjected to a load that exceeds the breaking load of the rupture lines 6, the exposed sheet portion 32 will fail along these rupture lines, For example, in the event of an explosion in the shielded region A, the exposed sheet portion 32 will tear along at least some of the rupture lines 6, allowing the blast loads (e.g. air and other gases at high pressure) to pass through the shielding device 30 and the opening O. Such rupture lines could be formed by weaving them into the fabric of the sheet, such as making the fabric weaker along the rupture lines compared to the fabric area adjacent the rupture lines. They could further be formed by forming (cg. stamping) perforations into the fabric, such as dotted perforations lines or dashed perforation lines.

Referring again to figure 1, the shielding device 30 also comprises a stationary structure 2 arranged proximal to the exposed sheet portion 32 and extending across the opening O, The stationary structure 2 is arranged on the side of the exposed sheet portion 32 facing the shielded region A; in other words on "the inside" of the sheet. The horizontal distance (or gap G) from the exposed sheet portion has been exaggerated in figure 1 for illustration purposes; this gap G should be comparably small when the sheet is in the condition as illustrated in figure 1. The stationary structure 2 has a texture that allows fluids (gases, liquids) to flow through it. In the illustrated embodiment, the stationary structure 2 comprises a mcsh of crossbars 12,13 and is made of met al or a composite material. The mesh size is dimensioned so as not to significantly impede the flow through the shielding device. The stationary structure 2 provides a structural backing for the exposed sheet portion 32, in that the sheet, when subjected to wind loads from the outside region B, may flex and bear against the stationary structure. The stationary structure, which has a substantially plane surface and is arranged parallel with the sheet, therefore enables the sheet to withstand the wind pressure from the outside region B. This wind pressure is effectively the stagnation pressure of an air flow, that under extreme weather conditions may have velocities around 250 km/h. Thus, in a practical application, the exposed sheet portion 32, backed by the stationary structure 2, will be able to withstand wind velocities of around 250 km/h (approximately 200 kp/m<2>) coming from the outside region B, and break along the rupture lines 6 when subjected to blast loads (e.g. caused by an explosion) on the order of e.g. 50 kp/m<2>coming from the shielded region A. If an explosion occurs in the shielded region A, the rollers serve as suspension devices for the sheet, and the sheet will be forced outwards by the explosion loads, and subsequently rupture along one or more of the rupture lines 6.

Retuming to figure 2, the sheet 1 comprises a number of sections håving different permeability. Reference numbers 16,17 and 18 designate sections with apertures 7, while reference number 25 designate the sheet without openings. The end portiona of the sheet, which are connected to respective rollers (in a manner which is known in the art), are typically of the latter section 25 configuration. The apertures 7 allow airflow through the exposed sheet portion 32 and thus allows for ventilation between the shielded region A and the outside region B. The sizc, shape and numbers of the apertures 7 vary on the different sections 16,17,18; giving the sections different ventilation properties by allowing different amounts of air to flow through the openings. The different ventilation properties allows for varying the ventilation of the shielded area A. The selection of the desired section (and hence the configuration of apertures 7) to constitute the exposed sheet portion 32 is accomplished by operating the rollers 3a,b, thus moving the sheet 1. The length (height) of each section 16,17,18 typically equals the vertical distance (height) between the upper and lower decks 4a,b.

When there is a need for creating good ventilation in the shielded region A, for example if a gas leak has been detected, the sheet is moved such that for example only section 18 (håving two comparably large apertures 7) constitute the exposed sheet portion 32. Conversely, if it is desired to reduce of even mirdmize airflow into the shielded region, the sheet may be moved such that section 16 or section 25 constitute the exposed sheet portion 32. This selection of sheet sections to constitute the exposed sheet portion may be based on input from human operators (activating the rollers) or by various sensors, such as wind sensors or gas sensors.

The air coming from the outside region B and passing through the ventilation apertures 7 may carry with it rain, snow, sleet or freezing rain. The apertures 7 and the meshed stationary structure 2 may create turbulence that serves to reduce the linear wind velocity somewhat, but these substances may still enter the shielded region A. Thus, in order to prevent such unwantcd substances from entering the shielded region A, while at the same time maintaining effective ventilation of that region, a secondary shielding device 31 is arranged behind the shielding device 30, as shown in figure 3.

The secondary shielding device 31 comprises a flexible secondary sheet 8 conncctcd to and stretchcd between two secondary rollers 10a,b, such that an exposed secondary sheet portion 34 is facing the shielding device 30. Referring additionally to figure 4, this secondary sheet 8 comprises sections 25' without openings, and an open section 11 with apertures 7', and a baffie section 19 with holes 35. The end portions of the secondary sheet, which are connected to respective secondary rollers 10a,b (in a manner which is known in the art), are typically of a section 25<1>configuration, without openings. Reinforcing wires 27 extend the length of the secondary sheet, one on each side. A suitable groovc (not shown) that is shaped and dimensioned to accommodate the wire ts provided on both ends of each secondary roller. This ensures a stable and controlled movement of the secondary sheet

The holes 35 in the baffie section 19 are formed by an open texture weave, and the holes are comparatively small such that a large number of holes 35 are provided. The holes 35 are dimensioncd to prevent the above mentioned unwanted substances from passing through. The baffie section 19 may additionally comprise a fleeced structure, in order to further absorb the wind energy. Snow, ice, freczing rain, etc, will also attach to this fleeced structure. The secondary sheet comprised a fireproof material and does not emit toxic gases when heated. The selection of the desired section 25', 19,11 of the secondary sheet 8 to constitute the exposed sheet portion 34 at any given time, is accomplished by operating the secondary rollers 10a,b, thus moving the secondary sheet 8. If, for example, the weather conditions are favorable, the secondary sheet may be operatcd such that the open section 11 with apertures 7' constitutes the exposed secondary sheet portion 34. In hostile weather, however secondary sheet is operated such that the baffie section 19 with holes 35 constitutes the exposed secondary sheet portion.

The secondary rollers 10a,b are aligned and in the illustrated embodiment attached to upper and lower deck structures 4a,b, respectively, similar to the rollers 3a,b of the shielding device 30. Although not specifically shown the figures, it should be understood that the axial length of the secondary rollers 10a,b corresponds to the width of the secondary sheet 8. The secondary sheet 8 has a length that exceeds the dimension of the opening O between the shielded region and the outside region, thus allowing parts of the secondary sheet to at any given time being stored on both secondary rollers 10a,b. The secondary sheet 8 may thus be moved up and down as indicated by the double arrow in figure 3, by rotating the secondary rollers 10a,b. The secondary rollers 10a,b may be rotated manually or by a control system comprising at least a motor (not shown). Thus, by operating the secondary rollers, different portions of the sheet 8 may exposed to face the shielding device 30; i.e. changing the exposed secondary sheet portion 34.

The secondary shielding device 31 further comprises upper and lower scraping devices 9a,b, each arranged in the vicinity of a respective secondary roller 10a,b. The scraping devices 9a,b are adapted to remove snow, sleet, freezing rain or ice from the exposed secondary sheet portion 34 when the secondary sheet 8 is being moved.

Both the shielding device 30 and the secondary shielding device 31 are arranged near an outer perimeter of the offshore installation, and placed such that ice, water, snow, etc., that are stopped by one or both of the devices (including being scraped off the sheet) drop into the sea and do not accumulate on the installation. If, however, the shielding devices are placed such that there are structures underneath, that prevent a free fall into the sea, one or more collection trays (not shown) in combination with auger conveyors (not shown) will move the accumulated substances to a discard chute. Pinching rollers (not shown) may be arranged between the lower scraper 9b and the lower roller 1 Ob, in order to squeeze liquids out of the secondary sheet.

On offshore installations, especially in a hostile environment, equipmcnt inspection and maintenance on a regular basis is necessary. Also, there is need for heating the air in the shielded region A to lcvels where operators can work in some comfort, even when the temperature in the outside region B is well below freczing. For this purpose, heating elements 20a,b are arranged between the shielding device 30 and the secondary shielding device 31, as illustrated in figure 5. The heating elements 20a,b will heat the air passing into the shielded region A due to wind pressure from the outside region B. The heating elements 20a,b may be a part of a high-pressurc fluid heating system. To save energy, the heating system may comprises a heat exchanger (not shown), where the return flow from the heating elements 20a,b passes through the heat exchanger in order to pre-heat fluid going out to the heating elements 20a,b.

Figure 6 is a front view of another embodiment of a first covering element 51 according to the invention. In particular, Figure 6 shows one section 52 which could be used additional to the sections 16,17,18 shown in Figure 2, or instead of one of the sections 16, 17,18. In Figure 6, the covering element 51 is shown without the wires 27 which would be attached to the longitudinal edges of the covering element as described in connection with Fig. 2 and projecting from the upper end in Fig. 6. In conncction with this embodiment, only aspects are described in which the covering element 51 distinguishes from the previously described covering element 1. Further, in Figure 6, not all elements are provided with reference numerals for reasons of clarity and comprehensibility, however, it should be clear for the skilled person that identically illustrated elements shall carry the same reference numerals.

The covering element 51 comprises a plurality of transverse laths 53 which extend straight in a transverse or horizontal direction (with respect to the intended use) of the

covering element 51. In the present example there are provided five transverse laths 53, however, the number may vary depending on required stability and size of the covering element 51. The benefit of the transverse laths 53 is that they maintain the shape of the covering element 51 when subjected to high tension. The transverse laths 53 will not fracture when the fabric is exposed to an explosion pressure exerted from the platform areas. Further, the covering element 51 is provided with ribbons 54 which extend straight along a longitudinal or a vertical direction (with respect to the intended use). In

Fig. 6 there are provided four ribbons 54, however, also their number may vary depending on required stability and sizc of the covering element 51. The advantage of providing the covering element 51 with the ribbons 54 is that they take most (or ali) of the longitudinal tension in the fabric of the covering element 51. These ribbons 51 will not fracture when the fabric is exposed to an explosion pressure exerted from the platform areas. The transverse lath and the ribbons 54 are preferably flexible and either attached to the fabric of covering element or woven into the fabric. The plurality of transverse laths 53 and the plurality of ribbons 54 form together a grid of horizontal and vertical struts, wherein in every one of the formed grid fields, fracture lines 56 extend from the four corners towards the respective grid field center.

The grid fields 55 of the covering element 51 which form the upper and lower row of all grid fields comprise rectangular openings 57 in their centers, respectively. The openings 57 are oriented with their longitudinal side along the longitudinal length of the covering element 51, and the corners of the rectangular openings 57 are rounded. The rounded corners have the benefit that they avoid stress hot spots when stress is applied to the covering element 51, e.g. by wind, explosions. From the middle of the longitudinal ends of the openings 57, fracture lines extend into each corner of the grid field 55, respectively.

The grid fields 58 of the covering element 51 which are located along the longitudinal edges of the covering element 51 and in between the grid fields 55 are provided with four rectangular openings 59 and one central oval opening 60, respectively. The openings 59 are also oriented with their longitudinal sides along the longimdinal length of the covering element 51, and their corners are rounded, but they are smaller than the openings 57. If a grid field 58 is imaginary divided into four areas by a central horizontal and vertical line, then the each of the openings 59 is located centrally in each of these four areas. From the middle of the longitudinal ends of the openings 59, which ends face away from the center of the respective grid field 58, fracture lines 56 extend into each corner of the grid field 58, respectively. From the middle of the other longitudinal end of the opening 59, fracture lines 56 extend to the opening 60, respectively.

The grid fields 61 which are located in the center of the covering element 51 and which are surrounded by grid fields 55 and 58 are provided with one central oval opening 62, respectively. From the opening 62, fracture lines 56 extend to each comcr of the grid field 61, respectively.

Regarding the forming of the fracture lines 56, the above description of fracture lines 6 applies. In this embodiment, the wcak region of the covering element 51 comprises the oval openings 60,62, the rectangular openings 57, 59 and the rupture lines 56.

As apparent from Fig. 6, the size of the substantially rectangular openings 57 and 59 vari es. The idea is that the size of the openings shall vary over the length of the covering element 51, i.e. depending on their location on the covering element 51 with respect to the longitudinal direction of the covering element 51. Depending on the size of the openings, the wind behavior of the covering element 51 changes. Further, the size of the oval openings 60 and 62 may also vary in the same manner as the rectangular openings 57 and 59.

For the vertical ribbons 54, a synthetic fiber material could be used, which has a strength of 4 to 7 times to the strength of steel and a very low specific weight. This material allows tightening the covering element 51 so that it has low vibration amplitude when exposed to the prevailing winds. A covering element 51 håving a width of e.g. 8 to 10 meters may be tensioned by several tons force (5 to 20 tons). This will ensure rapid vibrations (e.g. 10 to 20 Hz) with low amplitude, so that the sheet does not impinge on the vertical support structure behirid it.

The invention is particularly useful in hostile environments, with strong winds and temperatures well below freezing. Although the invention has been described with reference to an offshore installation configured for exploration, production, processing and/or storage of hydrocarbons, it should be understood that the invention shall be equally applicable for use on stationary and mobile onshore plants.

Claims

1. A ventilation and safety apparatus (30) for a facility håving a shielded region (A) at least partially defined by enclosing elements (4a,b); said apparatus (30) being arranged so as to delimit the shielded region from a region (B) outside the facility, and the apparatus (30) beingcharacterized by- a sheet-shaped covering element (1; 51) substantially covering an opening (O) between the regions (A, B) and håving a plurality of apertures (7; 57, 59,60,62) allowing fluid flow between the regions (A, B); - a stationary structure (2) håving a substantially planar configuration and comprising an open grid structure (12,13) in order to allow fluid flow through the stationary structure; the stationary structure furthcrmorc being arranged proximal to the covering element (1;

51) on the side of the covering element facing the shielded region (A); - the covering element (1; 51) and the stationary structure (2) being arranged in a substantially parallel relationship with a distance (G) between them, and arranged such that the stationary structure provides a support for at least a portion of the covering element (1; 51) when the latter is pressed towards the shielded region (A).

2. The apparatus of claim 1, wherein the covering element (1) comprises at least one weak region (6; 56) that is designed to be the first region of failure for the covering element.

3. The apparatus of claim 1 or claim 2, wherein the covering element (1) comprises sections (16,17,18; 52) håving apertures (7; 57, 59,60,62) of different sizes, and the area of each section corresponds substantially with the area of the opening (O).

4. The apparatus of claim 3, wherein the covering element (l; 51) is movable with respect to the opening, so as to arrange a selected one of the sections (16,17,18; 52) in the opening (O).

5. The apparatus of claim 4, wherein the covering element (1) is supported by and movable by rollers (3a,b) arranged on opposite sides of the operung (O); the rollers being configured for storing at least a portion of the covering element that is not being arranged in the opening (O).

6. The apparatus of claim 5, further comprising removal devices (5a,b) arranged proximal a respective roller (3a,b) and configured for removing substances such as snow or ice before the covering element is rolled onto a respective roller.

7. The apparatus of any of the preceding claims, wherein a secondary apparatus (31) is arranged on the side of the stationary structure (2) facing the shielded region (A); said secondary apparatus comprising a secondary flexible element (8) håving at least a baffie section (19) with a plurality of holes (25) that are configured to reduce the speed of the wind coming from the outside region (B) and stop unwanted substances from entering the shielded region (A).

8. The apparatus of claim 7, wherein the secondary flexible element (8) is movable so as to selectively arrange the baffie section (19) in alignment with the opening (O).

9. The apparatus of claim 7 or claim 8, wherein at least one hcatcr (20a,b) is arranged on the side of the stationary structure (2) that faces the shielded region (A).

10. The apparatus of any one of the preceding claims, wherein the covering element (51) comprises a plurality of transverse laths (53).

11. The apparatus according to claim 10, further comprising a plurality of vertical ribbons (54), wherein the transverse laths (53) together with the vertical ribbons (54) structure the covering element (51) in a plurality of grid fields (55, 58,61), wherein the at least one weak region comprises rupture lines (56) which extend from the corners of the grid fields (55, 58,61) towards the centers of the grid fields (55, 58,61), respectively.